Dr Margaret Chan
Director-General of the World Health Organization

World Health Days provide an opportunity to focus world attention on a health problem or issue that deserves special attention. Vector-borne diseases are one such problem.

Holding these diseases at bay, and getting the upper hand, require multiple actions on multiple fronts. These are especially tenacious diseases that deliver a stern reminder of the dangers of complacency.

The massive use of insecticides in the 1940s and 1950s successfully brought many important vector-borne diseases under control, including yellow fever and, in several areas, malaria.

Complacency set in. Control programmes were dismantled. Resources dwindled. Expertise was lost. And the diseases roared back with a vengeance, and a vanished infrastructure for their control. For example, the worldwide incidence of dengue has increased 30-fold compared with the situation 50 years ago.

Malaria, which is spread by mosquitoes, remains the best-known and biggest killer among vector-borne diseases. But there are others.

Some, like dengue and yellow fever, tend to erupt in large outbreaks that can paralyze health systems and cause considerable economic and social disruption. Onchocerciasis causes blindness. Chikungunya causes severe joint pain that can last for weeks.

Chagas disease in its late stage can cause heart failure and early death in young adults. Japanese encephalitis can permanently damage the central nervous system. Schistosomiasis, the most widespread of all these diseases, contributes to poor nutritional status and poor school performance.

Some forms of leishmaniasis are rapidly fatal. Others cause severe facial disfigurement. Of the 120 million people currently infected with lymphatic filariasis, around 40 million are disfigured and incapacitated by the disease.

Lost productivity is one consequence. Stigma and social exclusion are additional sources of misery, especially for women.

In another worrisome trend, vectors in several countries are developing resistance to a highly effective class of insecticides that is also the most affordable.

Vectors thrive under conditions where housing is poor, water is unsafe, and environments are contaminated with filth. Vector-borne diseases exact their heaviest toll on the poor, the people left behind by development. Measures that control the vectors provide an excellent, but underutilized opportunity to help these people catch up.

We need to recreate the momentum for vector control and the fundamental capacities that underpin it. These include staff with technical expertise, stronger surveillance systems, and better laboratory infrastructure.

For vector-borne diseases, control programmes never tread water. They either surge ahead or they sink.

This World Health Day is a reminder of the urgent need to act before an alarming situation deteriorates any further.

Taking action is entirely feasible. WHO promotes integrated vector management as the best approach to strengthen vector control. The approach uses a range of interventions, from indoor residual spraying to the use of natural insect predators, in combination and in a value-added way.

The control of vector-borne diseases can make a major contribution to poverty reduction, as it precisely targets the poor.

It is my sincere wish that this World Health Day will invigorate vector control and give it the high profile it deserves. No one in the 21st century should die from the bite of a mosquito, a sandfly, a blackfly, or a tick.